Techniques for creating content for cinema involve mixing digital audio signals to generate a digital audio soundtrack for presentation in combination with the visual component(s) of the overall cinematic presentation. Portions of the mixed audio signals are assigned to and played back over a specific number of predefined channels, e.g., 6 in the case of Dolby Digital 5.1 and 8 in the case of Dolby Surround 7.1, both industry standards. An example of a Dolby Surround 7.1 sound reproduction system is shown in FIG. 1.
In this example, the sound reproduction system includes 16 speakers for reproducing the mixed audio over 8 channels. The speakers behind the screen correspond to the left (L), center (C), right (R), and low frequency effects (LFE) channels. Four surround channels deliver sound from behind and to the sides of the listening environment; left side surround (Lss), left rear surround (Lrs), right rear surround (Rrs), and right side surround (Rss). In a cinema environment, each of the surround channels typically includes multiple speakers (3 are shown in this example) referred to as an array. Each of the speakers in an array is driven by the same signal, e.g., all 3 of the Lss speakers receive the same Lss channel signal.
Setting up such a system for playback in a particular room typically involves adjusting the frequency response of the set of speaker(s) for each channel to conform to a predefined reference. This is accomplished by driving each channel's speakers with a reference signal (e.g., a sequence of tones or noise), capturing the acoustic energy with one or more microphones (not shown) located in the room, feeding the captured energy back to a sound processor, and adjusting the frequency response for the corresponding channel at the sound processor to arrive at the desired response.
This equalization might be done, for example, according to standards promulgated by The Society of Motion Picture and Television Engineers (SMPTE) such as, for example, SMPTE Standard 202M-1998 for Motion-Pictures—Dubbing Theaters, Review Rooms, and Indoor Theaters—B-Chain Electroacoustic Response (©1998) or SMPTE Standard 202:2010 for Motion-Pictures—Dubbing Stages (Mixing Rooms), Screening Rooms and Indoor Theaters—B-Chain Electroacoustic Response (©2010), a copy of the latter of which is attached hereto as an appendix and forms part of this disclosure.